1. Field of the Invention
The present invention relates to a radiation-mounting structure of an electrical component having a heat generating property such as a relay or the like and a method for mounting an electrical component.
2. Description of the Related Art
Conventionally, because an electrical component or part using a large current such as a relay has a large calorific value, when the component is mounted on a board using normal eutectic soldering, deterioration of the soldered portion is remarkable.
Therefore, such means has been employed that a large current electrical component is mounted on a board with a resin-molded wire conductor through soldering, or high temperature solder is used or a radiating plate is provided when a normal board is used. Particularly, as the connecting structure of an electrical component, one which has been disclosed in Japanese Patent Application Laid-Open (JP-A) No. 11-40035 publication has been known. This art relates to a controller with a built-in relay, and a lead frame 1 made of a metal plate as a mounting board is used as a wire conductor. As illustrated in FIG. 1, in this conventional art, resin plates 2 and 3 are provided to sandwich the lead frame 1. Also, a burring portion 4 projecting downward in a substantially cylindrical shape is provided so as to penetrate the resin plate 3.
For example, a terminal 5A of a relay 5 is inserted in the burring portion 4 from the above of the resin plate 2, and the wire conductor and the relay 5 are connected to each other by filling solder 6 in the burring portion 4.
The solder 6 in a molten state is sucked up in the burring portion 4 by capillarity to be hardened. However, in the electrical component connecting structure, there is a drawback that the solder 6 which has been filled in the burring portion 4 can not be confirmed externally.
In view of the above, an electrical component connecting structure as shown in FIG. 2 has been employed. In this electrical component connecting structure, molded resin layers 8 and 9 are provided on a surface and a back surface of a bus bar 7 made of a metal plate, and the bus bar 7 at a position for mount/connection of an electrical component is exposed from the molded resin layers 8 and 9. A connecting hole 7A for insertion of a terminal 10 of an electrical component is formed at the portion of the bus bar 7 which has been exposed. FIG. 2 shows a state where a solder fillet 11 has been formed in a state where the terminal 10 of the electrical component has been inserted into the connecting hole 7A formed at the bus bar 7.
However, when dipping in a flow solder bath is performed in a state where the terminal 10 of the electrical component has been inserted in the connecting hole 7A formed in the bus bar 7, there occurs a problem that it is difficult to perform soldering in a normal flow solder bath due to that thermal capacity of the bus bar 7 is too large.
In view of the above, an object of the present invention is to provide an electrical component connecting structure of a wiring board where soldering work can be performed easily and which has a high reliability of connection.
According to a first aspect of the present invention, there is provided an electrical component connecting structure of a wiring board, where an electrical component is mounted on a surface side of a wiring board where an opening portion is formed at a predetermine position on an insulating material layer and a bus bar is provided along the insulating material layer, and a terminal of the electrical component and the bus bar facing the opening portion are soldered to each other, wherein the bus bar positioned so as to face the opening portion is formed with an insertion plate portion extending to a back surface of the wiring board along an inner wall of the opening portion and a connection plate portion, and the terminal and the connection plate portion are soldered at least at a back face side of the connection plate portion in a state where the terminal of the electrical component has penetrated the connection plate portion.
According to this arrangement, the bus bar arranged along the insulting material layer is led to the back surface side of the insulating material layer along the opening portion thereof, and the terminal of the electrical component is soldered to the connection plate portion formed at an end portion of the bus bar in a state where the terminal has penetrated the connection portion. Since the bus bar and the terminal of the electrical component are soldered at least between the back surface of the connection plate portion and the terminal which has penetrated the connection plate portion, electrical connection is securely performed. Also, in this manner, since the soldering is performed at least at the back face side of the connection plate portion, inspection about whether or not the soldering has been performed properly can be performed easily and securely. Furthermore, since the soldering is performed on the connection plate portion extending from the bus bar facing the opening portion, the soldered portion can be suppressed from being adversely affected by heating only the connection plate portion due to the magnitude of heat capacity of the bus bar.
Also, according to a second aspect of the invention, there is provided an electrical component connecting structure according to the first aspect, wherein the connection plate portion projects from the opening portion outside the back face thereof.
Accordingly, since the connection plate portion projects outside the back face of the opening portion, it becomes possible to confirm with eyes whether or not the connection plate portion and the terminal of the electrical component have been securely soldered to each other. In a case that the connection plate portion and the terminal are soldered to each other, since the connection plate portion and the terminal can securely be dipped in a flow solder bath, the temperature of the connection plate portion is increased up to that of the solder or so in a short time so that soldering work can be performed rapidly.
Furthermore, according to a third aspect of the invention, there is provided an electrical component connecting structure according to the first or second aspect, wherein the connection plate portion is formed with an opening portion for terminal connection which the terminal penetrates. Thereby, soldering work can be performed in a state where the terminal of the electrical component has been inserted into the opening portion for terminal connection formed at the connection plate portion. In this case, since molten solder also attaches to a surface side of the connection plate portion by capillarity from a gap between the opening portion for terminal connection and the terminal, the connection plate portion can be soldered at its surface and back surface to the terminal.
According to a fourth aspect of the invention, there is provided an electrical component connecting structure according to one of the first to third aspects, wherein the insulating material layer is an insulating plate formed of insulating resin. Therefore, since the bus bar may be assembled along the insulating plate, manufacturing of a wiring board can be facilitated.
Furthermore, according to fifth aspect of the invention, there is an electrical component connecting structure according to one of the first to third aspects, wherein the wiring board is formed by insert-molding the bus bar with insulating resin. Accordingly, since the bus bar is formed by insert-molding with insulating resin, the electrically insulating property of the bus bar can be improved. For this reason, reliability of connection of an electrical component to a wiring board can be improved.